CD disaster relief

CD recorders sometimes fail to successfully record a disc, usually with an error known as a "Buffer underrun." Sometimes, a disc may fail when adding additional data to a previously recorded "multisession" or "DirectCD" disc, causing all the data on the disc to become unreadable. This article presents a discussion of why discs fail and solutions to the problem.

Click here for information on what to do about scratched or dirty discs.

Why Discs Fail
There are a number of reasons why discs fail. The primary cause of "sudden failure" in a disc that was previously readable is due the nature of the dyes used in recordable CD-R media. These discs fall into three categories:

• Azu (blue) dye. Patented by Verbatim.
• Cyanine (green) dye. Patented by Taiyo Yuden; and
• Phthalocyanine (gold stabilized clear) dye; patented by Mitsui.

As described in a feature on the topic at www.macintouch.com, all brands of CD-R media use one of these forms of dye, or a hybrid mix. There are, however, several other factors, including the density and evenness with with the dye is applied, the conditions in which the disc is stored (cool, dark locations with low humidity are best) and the condition of your CD recorder. In fact, different recorders have differing abilities to read the darkened spots that their write-mode laser has etched into the disc. Some discs have dark dyes that aren't read well by the read-mode lasers of some drives; other discs -- often these with a silver surface -- are too shiny to be reliably read. Indeed, some brands of CD recorders work fine with a type of media that is useless in a different recorder.

There are, however, certain brands and types of discs that are better than others. Phthalocyanine dye is considered the most stable of the dye types, and cheap green dye CD-R discs are considered the worst. Generally speaking, gold-surface discs with Phthalocyanine dye from an ISO9660-certified major manufacturer are your best bet.

Help for Disc Disasters
The first tool we saw on the market that specifically addressed the issue of damaged CD-R discs was Adaptec's ScanDisc utility for DirectCD discs. Unfortunately, we've yet to recover a single disc using this program. Clearly, there is a market opportunity for other solutions.

Freeware
CDmage is a freeware tool from "TWoeMS." It features support for Mode1/2048, Mode1/2352, Mode2/2336, Mode2/2352, CDI/2352, CDI/2336, CD+G/2448, and Audio/2352 tracks. You can open and browse (play) CUE, BIN, ISO, MM2, PCM, WAV, FCD, VCD, TAO and NRG files, as well as extract and convert tracks into any compatible supported format. You can extract files from data tracks or compare files with files burned on the CD or with files on the hard drive and scan checkable tracks for corruption. With this software you can change volume label and other CD identification data along with the ability to repair corrupted sectors or locate content of corrupted sectors. You can play audio tracks direct from BIN/ISO file without extraction while scanning, repairing, locating errors and sector browser with sector field highlighting. Download CDmage 1.0 Beta XVI from Betanews.com.

IsoBuster
IsoBuster lets you explore a CD's File System while bypassing Windows. This way you get better error handling and several retry-mechanisms to aid you in getting the data anyway (or at least partially), more CDs stay 'readable' after problems (such as Buffer Underrun), read and extraction from CD-i, VCD, SVCD, CD-ROM, CD-ROM XA, DVD, and DVCD. Download it here.

DVD-RAM solutions
SAI is currently promoting the FixDVD! utility, announced Feb. 24, 2000, as a key feature of its WriteDVD! 2000 upgrade. It shouldn't be too difficult for the company to develop a variant of this tool for CD-R and CD-RW users. Such a product could prove a compelling solution to problems frequently encountered by users of Adaptec's market-leading "DirectCD" CD-R and similar UDF-based CD-RW technologies. Such a product could potentially capture a utility market share for the CD-Rewritable market similar to that enjoyed by Symantec's Norton Utilities, which currently lacks the ability to fix any type of UDF-based CD. Although SAI might not be the company best able to carry this product to a market-leading position, the potential for a spin-off product or company exists.

Scratched or Dirty Discs

1. Holding the CD by its edge, wipe it with a link-free cloth or tissue that has been dampened with a 50/50 solution of isopropyl alcohol and distilled water (commercial preparations are available, under a variety of brand names including "WipeOut CD Repair Kit," available from www.cdrepair.com), then dry it. Wipe gently from the center of the disc straight out to the edge. Do not wipe in a circular motion and never buff the disc.
2. Check the disc to see if it works. If it does, copy the data onto your hard drive and burn another copy.
3. If the disc still doesn't work, it's time for a little more aggressive scratch-removal. Dampen your cloth and apply a small amount of toothpaste to it. Gently rub the abrasive on the scratch, working from the center straight out to the edge. Don't worry if the scratch doesn't completely disappear -- it doesn't need to.
4. Rinse of the toothpaste with your isopropyl alcohol and distilled water solution and wipe dry. Check the disc and back up the data if possible; if it still doesn't work, try again, rubbing a little harder.

For Further Reading

• (Aug. 27, 2000) CD Facts - Information on the care of CD discs.
• (July 3, 2000) http://www.macintouch.com/cdrfailure.html - Why failures occur, what types of discs hold their data the longest and other topics.
• (July 3, 2000) Additional tech info (including details on "gold on gold" media): SyntheMedia
• For more info on CD-R technology, see http://www.fadden.com/cdrfaq/.
• (Aug. 27, 2000) CDR technical info - A description of the "Orange Book" standard, which describes the specifications for CD-Write Once (CD-R) technology.